Most people know that if you have a spinning object, the outside of it rotates faster than the inside of it. If you had a rod, say, a light year long, and got it spinning fast enough at the center, could the ends of the rod exceed light speed?
As objects approace the speed of light (denoted c)their mass is distorted. Therefore, the end of the rod could not travel faster than c.
The old spinning object dodge ignores the fact that inertia applies to spinning objects just as it does those moving through a frame of reference. No free lunch.
As previously stated, no.
What would happen is that the ends would break off from due to the increased mass. Or (assuming a somewhat flexible rod) the rod would bend into a spiral until the ends came close enough to the center that breaking the speed of light would no longer be an option.
If neither of these is an option, then you’ll have a rod that no amount of force could get spinning fast enough to achieve the result you desire.
I could have sworn we covered a similar subject in GQ before, but I haven’t been able to find it. I believe they used a disk instead of a rod.
God is my co-pilot. Blame Him.
Look, the problem is that your question is ambigous. You can’t just ask whether X would be moving faster than the speed of light, you must ask faster than the speed of light relative to a particular observer. That’s the point of the special theory. Relative to the person at the center, the end would not be moving at all. They would be measured as being rigid–neither moving away or closer, to the left or to the right. relative to someone standing above the rod, she would not judge the ends to be exceeding the speed of light. Her measurement of the speed of the center of the rod would be proportionaly slower. Could she increase the spped at the center? Only to a point as she would judge the mass of the rod to increase as it rotated.
The bottom line is you can’t “exceed” the “speed” of “light” because all these terms are internal to the special theory, which makes their consistency a tautology.
tony1234
Two things fill my mind with ever-increasing wonder and awe: the starry skies above me and the moral law within me. – Kant
tony1234, the speed of light is an absolute limit. There are certain situations were you can argue in favor of an exception, but… well… I think it’s best that you just read the following:
Usenet Relativity FAQ: Is Faster Than Light Travel or Communication Possible?
In regards to the OP, the answer is also included in the article above, under the section of rigid bodies. Hope that helps.
{{{Most people know that if you have a spinning object, the outside of it rotates faster than the inside of it.}}}—C Monkey
Unless, of course, you consider angular velocity.
–Kalél
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